Eosinophils are pleiotropic multifunctional leukocytes involved in initiation and propagation of diverse inflammatory responses, as well as modulators of innate and adaptive immunity. They represent a small percentage of the total white blood cell population and are recruited from the bone marrow into the circulation to inflammatory foci and activated by various cytokines, chemokines and adhesion molecules (Hogan et al., Clin. Exp. Allergy 38: 709-750 (2008)). Activated eosinophils release toxic compounds from their granules and secrete inflammatory and regulatory cytokines, chemokines, and growth factors, including many potent inducers of immune responses in asthma, eczema, rhinitis, and other inflammatory diseases (Hogan et al., 2008, supra). Eosinophils are a major component of the inflammatory response observed in asthma and they are often the dominant inflammatory cell present in the bronchi of asthmatics (Lee et al., Science 305: 1773-1776 (2004)).
Eosinophilia, or abnormally high eosinophil counts in the blood or body tissue, can be caused by conditions or diseases including, eczema, leukemia, autoimmune diseases, asthma, allergic rhinitis (hay fever), and parasitic infection, as well as certain side effects of drugs. Without treatment, high numbers of eosinophils can accumulate in the heart and other organs, which can lead to nerve damage, heart failure, lung disease, and blood clots.
While methods of treating eosinophilia and conditions causative of eosinophilia are known in the art, there remains a need for methods of determining a susceptibility to such conditions.